Automatic and semi-automatic firearms, such as a standard AR-15 and the like, are operated using a gas impingement system. The gas impingement system directs gas from a fired cartridge into an interior region of the bolt carrier assembly (i.e., an impingement chamber directly behind the bolt) to cycle the firearm, i.e., to drive back the bolt carrier assembly ejecting the spent shell. In particular, in a standard AR-15 firearm, for example, the gas is vented directly into the interior of the bolt carrier assembly into an impingement chamber directly behind the bolt to force the bolt carrier assembly rearward. One problem with such a direct gas impingement system is the gas, which is hot propellant gases, carries carbon and other debris (e.g., powder residue) that over time can build up on the bolt and bolt carrier in the interior of the bolt carrier assembly and potentially slow down and/or stop the operation of the bolt and carrier. This may occur even with frequent cleaning and the operation of the bolt and carrier may slow and/or stop operation during long periods of use.
Further, these gases that are vented into interior region of the bolt carrier assembly enter at very high temperatures. These hot gases accelerate the breakdown of the various lubricants and coatings in the bolt carrier assembly, which, again, over time increases wear tear of the firearm, thus, shortening its lifetime and increasing its likelihood of failing during operation (e.g., jamming).
Therefore, there is a need for a gas impingement system that reduces or eliminates the buildup of carbon and debris on the bolt and bolt carrier in the interior region of the bolt carrier assembly. There is also a need for a gas impingement system that will reduce or eliminate the degradation of the various lubricants and coatings in the bolt carrier assembly caused by exposure to such high temperatures gases.